Calculate Free Testosterone with TruT by FPT

[Deleted member 16042]

Same.

New info is huge. I was rockin T in the mid 700s but got told since my free t direct was 8 that trt would help me. Shbg was in the 80s...at least that’s down to 45 now

With my original scenario my tru T was 20+, not 8...live and learn. Didn’t know about the different free T test accuracy issues back then.

Confusing to me that if TruT is a wild mismatch with Free direct whether the relative ranges mean much at all related to how you actually feel symptomatically.

So many moving targets trying to base anything on the numbers. It seems slippery diagnostically

 

[Cataceous]

Understood, I get that, so wondering if my good doctor (Saya) is dropping free T blood work in favor of TruT calcs and adopting 164 to 314 pg/ml reference range?

I think this should be the way of the future. The testing labs are part of the problem because they bundle the direct free T test with total T for a low price, encouraging its use.

Confusing to me that if TruT is a wild mismatch with Free direct whether the relative ranges mean much at all related to how you actually feel symptomatically.
...

Calculated free T is so consistent that I've been comfortable identifying a spot on the Vermeulen scale (10 ng/dL) as a threshold, below which guys may start to have symptoms of low testosterone. I'll just have to teach myself to start thinking in the TruT scale, which is about 50% higher. But it's just a multiplicative factor.* With the direct free T tests you can get gross inconsistencies that leave you scratching your head, and this is demonstrated in various research studies.

[*Edit: It's not nearly so simple, because if there is a linear factor across different testosterone levels then it is at least dependent on SHBG. E.g. when SHBG is 30 nmol/L then Vermeulen free T ~= 2/3 TruT, but with SHBG at 10 VcfT ~= 0.9 TruT, for albumin at 4.3]

 

[DragonBits]

Yeah I know, I've been with Saya for a couple years, but with this new info I wonder if his perspective will change.

It would actually be helpful to me to drop free T direct testing in favor of CMP which has albumin as I'd like to monitor liver due to taking green tea extract. Just would be nice to trade off costs. I know CMP is only $15, but cumulative costs add up in a big way for me.

Regardless of the free T direct test, don't you still need to know your total T?

In order to use the TruT site, you need to know your total T levels. So I don't see why you can drop T testing, whether it's free T or total T.

 

[fifty]

I wish i knew direct free t was awful. I would have gladly paid another $60 for free t ultrafiltration.

 

[Deleted member 16042]

Regardless of the free T direct test, don't you still need to know your total T?

In order to use the TruT site, you need to know your total T levels. So I don't see why you can drop T testing, whether it's free T or total T.

I was not suggesting to not test for total T, only drop the added "with free T"

 

[DragonBits]

I was not suggesting to not test for total T, only drop the added "with free T"

Well, there isn't any total T test that is cheaper than the $35 that includes the free T.

They do have a LC/MS test for total T, but that is $106.

 

[Deleted member 16042]

Well, there isn't any total T test that is cheaper than the $35 that includes the free T.

They do have a LC/MS test for total T, but that is $106.

OK. Not sure if that is true for my tests which are done through insurance at their rates, but let's drop it... moot in context of this discussion, sorry I brought it up.

 

[DragonBits]

I wish i knew direct free t was awful. I would have gladly paid another $60 for free t ultrafiltration.

Why I always thought the free T test was good enough for medical work. It does seem to track with total T and shbg.

I wouldn't want to pay more for increase accuracy, as I don't think I would do anything different. But I would never just get the free T test as I pay a lot more attention to the total T.

When I was on my own, I was using Nebido which you don't "adjust" your levels, I only tested total T twice in 5 years, never E2, and PSA a couple of times.

Coming from that experience, I am a little more cavalier about tests.

Even so, I have tested quite a few times since 2016, but not sure I really needed it, but now as least I have a pretty good idea of what level I will be at assuming I do x or y.

I would like to test E2 right now as I think it's at least 35 pg/ml and I am curious. My recently tested SHBG is 73.6 which should limit how much E2 I have. My guess is my total T is around 1300-1400.

 

[in_TRT]

It looks to me as though you could multiply the Vermeulen values by an appropriate constant and the results would be almost as good—or am I missing something?

Not so.. Figure 5 seems to show that there is no direct (linear) correlation. I may be wrong!!

 

[in_TRT]

The direct free T assays should not be used, period. Not only are they on an entirely different scale, by an order of magnitude, but they also do not correlate well with either equilibrium dialysis or ultrafiltration. In short they are just plain inaccurate. The TruT calculation correlates well with the high-quality tests and is on virtually the same scale. The Vermeulen free T calculation correlates well with the good tests, but is effectively on a lower scale.

Vermeulen was proposed on simplified assumptions before even the structure of SHBG was known..

 

[Cataceous]

Not so.. Figure 5 seems to show that there is no direct (linear) correlation. I may be wrong!!

If they both correlate well with equilibrium dialysis then presumably the cross-correlation holds:

A robust correlation was noted ... for [Vermeulen calculated free testosterone] and [equilibrium dialysis] (r = 0.986).

Ref.
And if you look at figure 4A you can see how the deviation appears to be in the slope magnitude.

 

[in_TRT]

If they both correlate well with equilibrium dialysis then presumably the cross-correlation holds:
Ref.
And if you look at figure 4A you can see how the deviation appears to be in the slope magnitude.

The older papers have too many simplistic assumptions. I quote the text from figure 2 of the paper you cited: Figure 2. Bland–Altman plots comparing cFT (right) and RIA (left) against EqD. Mean bias is 0 [95% CI 29.4 to 29.4] for RIA and -19.4% [95% CI 45 to 6.1] for cFT.
How do we reconcile such information in papers supporting Vermeulen?

SHBG and T doesn't seem to have a fixed single affinity, which would make sense (in nature's design). Inverse relationship between hSHBG affinity for testosterone and hSHBG concentration revealed by surface plasmon resonance. - PubMed - NCBI

The problem is very few studies have actually tried to ask the question on accuracy in the last 40 years!!! Problems with the simple model of Free T calculation are well known that is why people have been developing empiric equations for computing free T. I will try to dig some other refs...

 

[Cataceous]

Not so.. Figure 5 seems to show that there is no direct (linear) correlation. I may be wrong!!

After playing with the numbers some more I think you're right. In the couple cases I looked at, if one makes SHBG and albumin constant then there is a roughly linear relationship between Vermeulen and TruT. But there's definitely not a direct linearity that holds across all variables.

 

[Deleted member 16042]

New labs in, Free direct 23.4, 1.29X higher than top of range (18.1), Tru-T 38 1.22 higher than normal range (31), ~6% difference between methods relative to normal range.

 

[madman]

New labs in, Free direct 23.4, 1.29X higher than top of range (18.1), Tru-T 38 1.22 higher than normal range (31), ~6% difference between methods relative to normal range.

Again the proper way to do a comparison would be to use the measured methods:

gold standard Equilibrium Dialysis or Ultrafiltration results compared to the direct immunoassays.....than you would see the big difference and how inaccurate the direct immunoassay and tracer analog testing methods are when compared to the gold standard.

I should have been more specific as in many examples I am showing the results using members direct immunoassays (measured) compared to the newer calculated TruT method only because the accuracy of the TruT calculated method is on par with results using the measured gold standard Equilibrium Dialysis.

By using the newer calculated TruT method I am basically showing them what their FT levels would truly be if they had the more accurate gold standard Equilibrium Dialysis done.

So when using the TruT calculated method results .....they should be very similar to the results one would get when testing using the measured gold standard Equilibrium Dialysis.

Problem is most are just getting the cheap inaccurate direct immunoassay for FT as oppose to the more accurate testing methods Equilibrium Dialysis or Ultrafiltration....so they can never compare the direct immunoassay results to the gold standard Equilibrium Dialysis to truly see the difference in what their FT levels truly are.

You have the results from the measured direct immunoassay and using the newer calculated TruT.....you would now need to test FT again using the measured Equilibrium Dialysis or Ultrafiltration and than compare the results with the direct immunoassay and you will see the difference between the measured methods and when looking at overall results the TruT calculated FT results should be very close to Equilibrium Dialysis FT results as oppose to the direct immunoassay results.







April 22/2019

Blackhawk said:
Mind blown. I am utterly confused.
...
When converted that's 351.6 pg/ml compared to direct at 18.8 pg/ml

So are we looking at an entire revamp of the direct assay pg/ml reference? Different method, utterly different range?


Cataceous replied:

"The direct free T assays should not be used, period. Not only are they on an entirely different scale, by an order of magnitude, but they also do not correlate well with either equilibrium dialysis or ultrafiltration. In short they are just plain inaccurate. The TruT calculation correlates well with the high-quality tests and is on virtually the same scale. The Vermeulen free T calculation correlates well with the good tests, but is effectively on a lower scale"

 

[Deleted member 16042]

Again the proper way to do a comparison would be to use the measured methods:

gold standard Equilibrium Dialysis or Ultrafiltration results compared to the direct immunoassays.....than you would see the big difference and how inaccurate the direct immunoassay and tracer analog testing methods are when compared to the gold standard.

I should have been more specific as in many examples I am showing the results using members direct immunoassays (measured) compared to the newer calculated TruT method only because the accuracy of the TruT calculated method is on par with results using the measured gold standard Equilibrium Dialysis.

By using the newer calculated TruT method I am basically showing them what their FT levels would truly be if they had the more accurate gold standard Equilibrium Dialysis done.

So when using the TruT calculated method results .....they should be very similar to the results one would get when testing using the measured gold standard Equilibrium Dialysis.

Problem is most are just getting the cheap inaccurate direct immunoassay for FT as oppose to the more accurate testing methods Equilibrium Dialysis or Ultrafiltration....so they can never compare the direct immunoassay results to the gold standard Equilibrium Dialysis to truly see the difference in what their FT levels truly are.

You have the results from the measured direct immunoassay and using the newer calculated TruT.....you would now need to test FT again using the measured Equilibrium Dialysis or Ultrafiltration and than compare the results with the direct immunoassay and you will see the difference between the measured methods and when looking at overall results the TruT calculated FT results should be very close to Equilibrium Dialysis FT results as oppose to the direct immunoassay results.







April 22/2019

Blackhawk said:
Mind blown. I am utterly confused.
...
When converted that's 351.6 pg/ml compared to direct at 18.8 pg/ml

So are we looking at an entire revamp of the direct assay pg/ml reference? Different method, utterly different range?


Cataceous replied:

"The direct free T assays should not be used, period. Not only are they on an entirely different scale, by an order of magnitude, but they also do not correlate well with either equilibrium dialysis or ultrafiltration. In short they are just plain inaccurate. The TruT calculation correlates well with the high-quality tests and is on virtually the same scale. The Vermeulen free T calculation correlates well with the good tests, but is effectively on a lower scale"

Yeah I get it Madman, and do not have the same confusion I did in April.

I am only posting to share N=1 comparison of my actual labs and Tru-T. I am assessing in my own case how Free T direct possibly relates to Tru calc.

Free T direct is what my doctor orders, but from here on I will be requesting ongoing CMP for reasons other than doing Tru-T calcs, but that ends up a benefit having albumin, so can do it anyway. I will track my N=1 case of Free direct vs Tru-T relative to their respective ranges.

And for the record, this is in no way argument for or against anything.

 

[madman]

 

[xqfq]

While this calculator is, I’m sure, much better than he existing alternatives, I wonder if it’s missing some possible variables.

Most notably, I’ve read about how magnesium effects SHBG <-> Testosterone binding affinity. According to this paper:

The Interplay between Magnesium and Testosterone in Modulating Physical Function in Men

“Excoffon and colleagues provided evidence of a magnesium-mediated variation in the T-SHBG affinity. The change in magnesium levels inside the biological serum concentration range (0.75–0.95 mM) could lead to an enhancement of the Bio-T. In fact, the affinity of T to SHBG seems to change slightly with the magnesium concentration. Magnesium binds SHBG in a nonspecific mode, leading to an uncompetitive inhibition with T in binding SHBG and to a subsequent enhancement of Bio-T availability.”

So based on this paper, serum magnesium concentration may be a necessary variable for accurate free testosterone calculation.​

I believe boron works in a similar way, increasing the availability of magnesium somehow.​

I know the researchers showed their TruT model matching closely with the better free T blood tests, but I wonder if there would be a discrepancy in individuals who heavily supplement magnesium or are otherwise more deficient in magnesium.

 

[DragonBits]

Same.

New info is huge. I was rockin T in the mid 700s but got told since my free t direct was 8 that trt would help me. Shbg was in the 80s...at least that’s down to 45 now

With my original scenario my tru T was 20+, not 8...live and learn. Didn’t know about the different free T test accuracy issues back then.

Anyone correct me if I am wrong? @madman and others.

Your FT with the cheap immunoassay was 8, but the range is 6.6-18.1,
Your FT with TruT was 20+, but the range is 16-31.

So with immunoassay, you were 21% off the bottom of the range.

With Trut you were 25% off the bottom of the range.

In both ways of measuring FT, you were near the bottom but not such a dramatic difference with comparing to the ranges for both.

Did I make a mistake about this?

 

[xqfq]

Anyone correct me if I am wrong? @madman and others.

Your FT with the cheap immunoassay was 8, but the range is 6.6-18.1,
Your FT with TruT was 20+, but the range is 16-31.

So with immunoassay, you were 21% off the bottom of the range.

With Trut you were 25% off the bottom of the range.

In both ways of measuring FT, you were near the bottom but not such a dramatic difference with comparing to the ranges for both.

Did I make a mistake about this?

It's a great question.

Based on my reading of madman's post about the range, I believe it's the "16-31" range isn't a "95% of people fall into this" sort of range but rather the "therapeutic target" range. So it's something like, if you're in that 16-31 range, you may not have hypogonadal symptoms.

That's my reading at least.